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Optimal Use of Supercritical CO 2 as Heat Transfer Fluid for Geothermal System

Author

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  • Chengcheng Liu

    (State Key Laboratory of Deep Geothermal Resources, Beijing 102206, China
    Sinopec Key Laboratory of Geothermal Resources Exploitation and Utilization, Beijing 102206, China
    Sinopec Research Institute of Petroleum Engineering Co., Ltd., Beijing 102206, China)

  • Lianzhong Sun

    (State Key Laboratory of Deep Geothermal Resources, Beijing 102206, China
    Sinopec Key Laboratory of Geothermal Resources Exploitation and Utilization, Beijing 102206, China
    Sinopec Research Institute of Petroleum Engineering Co., Ltd., Beijing 102206, China)

  • Lei Wang

    (State Key Laboratory of Deep Geothermal Resources, Beijing 102206, China
    Sinopec Key Laboratory of Geothermal Resources Exploitation and Utilization, Beijing 102206, China
    Sinopec Research Institute of Petroleum Engineering Co., Ltd., Beijing 102206, China)

  • Weiqiang Song

    (State Key Laboratory of Disaster Prevention and Ecology Protection in Open-Pit Coalmines, Shandong University of Science and Technology, Qingdao 266590, China)

  • Zhicheng Yu

    (State Key Laboratory of Disaster Prevention and Ecology Protection in Open-Pit Coalmines, Shandong University of Science and Technology, Qingdao 266590, China)

Abstract

Supercritical carbon dioxide (CO 2 ) is a promising working fluid for geothermal energy extraction due to its superior heat extraction capacity and high fluidity within reservoirs. However, significant thermal energy is lost during transportation along the production well. This study develops a mathematical model coupling heat transfer and CO 2 compressibility to investigate strategies for improving heat transfer efficiency from the reservoir to the surface. The influence of mass flow rate (20 kg/s; 25 kg/s and 30 kg/s) and outlet back pressure (8 MPa; 9 MPa and 10 MPa) on system performance is evaluated. Results indicate that the amount of geothermal energy delivered to the surface increases linearly with mass flow rate. Compared to water, CO 2 exhibits a 65.5% greater temperature drop along the wellbore but reduces the pressure drop by 50%. A lower outlet back pressure is recommended to enhance both heat transfer and operational safety. The model offers valuable insights into assessing the geothermal potential of depleted high-temperature gas reservoirs.

Suggested Citation

  • Chengcheng Liu & Lianzhong Sun & Lei Wang & Weiqiang Song & Zhicheng Yu, 2026. "Optimal Use of Supercritical CO 2 as Heat Transfer Fluid for Geothermal System," Sustainability, MDPI, vol. 18(1), pages 1-19, January.
    • Handle: RePEc:gam:jsusta:v:18:y:2026:i:1:p:483-:d:1832294
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